Celtic have been lauded for their Champions League performances but Neil Lennon's team have only fleetingly endorsed their status as the overwhelming favourites for the Scottish Premier League.

Barcelona's visit to Glasgow on Wednesday is eagerly anticipated, not least because Celtic's hopes of progression to the last 16 remain firmly alive. Yet they have not handled the reality of prominent European fixtures interspersed between routine domestic games. Since playing admirably in defeat at the Camp Nou, Celtic have dropped five SPL points.

The 2-2 draw at Dundee United on Sunday returned the champions to the summit on goal difference but there was a return of the sloppiness that will perturb Lennon. Barça, needless to say, will punish heavily any similar frailties.

Celtic led 2-0 heading into the final minute but shipped two goals against a side who had offered virtually nothing in attack until that juncture.

In different seasons, Celtic's tally of 21 points from 11 league outings would trigger concern but this is now a Scottish top flight minus Rangers and lacking a team who can mount a meaningful challenge to Celtic for the championship.

The prominence of Hibernian is welcome with the wider picture in mind but will not last. Celtic will never use Champions League distractions as a mitigating circumstance for their occasionally lethargic approach at home, even if the evidence suggests otherwise.

In this instance, Lennon was unwilling to castigate his team. Perhaps in his heart of hearts and with regard to the grand scheme, the Celtic manager knows a draw at Tannadice is not particularly damaging.

"I am very frustrated because we were brilliant," Lennon said. "I just think we were unfortunate. We were excellent on a sticky pitch. We didn't get what we deserved, which was three points. Other people out there will criticise us but I won't. That performance was good."

Lennon also has injury concerns to occupy his mind. Gary Hooper, James Forrest and Georgios Samaras – all influential Celtic performers in Europe – missed the United game. Thomas Rogne and Emilio Izaguirre started but limped from the fray with calf and hamstring troubles respectively; Lennon conceded all are doubts for Barça's visit. "We are starting to collect some niggles which is disrupting the flow of the squad," he said.

A dismal first half was notable only for Celtic wasting two fine chances, Rogne and Scott Brown the culprits. Izaguirre passed up another opportunity within seconds of the restart and it was the man sent on to replace the full-back, Miku, who broke the deadlock. Tony Watt, who has impressed since his introduction into the Celtic attack, played in the Venezuelan who offered a fine, dinked finish.

Watt scored a goal of his own after the United goalkeeper, Radoslaw Cierzniak, played an attempted clearance right to the 18-year-old's feet.

From there, Celtic seemed set for victory but a lack of concentration undid their earlier work. After they failed to handle a long throw-in, Gary Mackay-Steven scored from 12 yards.

Worse was to follow for Lennon. Efe Ambrose, a Celtic central defensive substitute, looped a header past his own goalkeeper from a Barry Douglas cross. Once again, it was an unnecessary act of generosity from Celtic.

Peter Houston, the United manager, was content with an unlikely draw but irked over the impasse between the Scottish Football Association and the national manager Craig Levein.

An announcement is due on Monday over whether Levein will remain in office, with the SFA board split over his future.

Houston has acted as Levein's international assistant on a non-contract and part-time basis. Monday will be the 20th day since Scotland went down 2-0 in a World Cup qualifier in Belgium and Houston said that is too long to keep Levein hanging on.

"If the SFA decide that they want to remove Craig, it shouldn't take three weeks or so to remove him," he said. "I think that they've let the thing settle, they've had discussions, but they've had the discussions for a few days. It shouldn't take that long to make that decision.

"Fair enough, the SFA were wanting to let the whole situation calm down a bit before discussing that. But now they have discussed it over two days and I am going with what I am reading and hearing. It shouldn't be that hard to make that decision."